Research has challenged the perception that the rate of childhood obesity is increasing.

A study by the University of South Australia has compared data from the most recent national survey of children's nutrition and physical activity to the previous one in 1995.

It has found that obesity rates among children levelled off in the late 1990s and have been steady since.

The authors also looked at 28 studies of childrens' height and weight that had been conducted in Australia since 1985.

Professor Tim Olds, from Uni SA, says one in five children is still battling with weight issues, but that is no greater than a decade ago.

"If you had a look at the data until certainly the early 2000s and you put them all together, it really did look as if things were increasing exponentially - there was a runaway increase in overweight and obesity," he said.

"So it's not that these people misinterpreted the data, it's just that recent data has shown a change in the pattern.

"When we put all those studies together, and they encompass about 70-80,000 children, what we noticed was there was a very clear flattening out of the prevalence the rate of overweight and obesity in children, it started in the late 90s and it's continued until today."

Professor Olds was quick to point out that the survey did not mean childhood obesity was not a serious problem in Australia.

"The best way to charcterise it is, the patient is critically ill but isn't getting any worse," he said.

"I think it's a very serious situation. Five to 6 per cent of children are classified as obese and a further 15 to 20 per cent are characterised as overweight.

"That's a very large slice of Australia's children that weigh more than they should."